Pneumatic rubber tires conventionally have two spaced apart, relatively inextensible beads, usually composed of twisted, or cabled, metallic wires, which are surrounded by rubber components. A significant component which is conventionally positioned around a portion of the bead is the chafer. The chafer is a rubber composition conventionally designed to contact a rigid wheel rim and, therefore, interface between the tire and rim. Rather obviously, the chafer rubber composition must normally be very abrasion resistant, tough, and have a relatively high modulus while also having acceptable flex and rubber fatigue properties as well as having good resistance to cut growth.
The chafer rubber composition is conventionally composed of a diene-based rubber composition which is carbon black reinforced. The chafer rubber composition may optionally contain a textile fabric reinforcement for dimensional stability, where the textile fabric portion of the chafer is conventionally adjacent to the bead portion of the tire, leaving the rubber portion of the chafer to contact the rigid wheel rim when the tire is mounted on such rim and inflated.
Pneumatic tire chafers, their intended interface between the tire bead and rigid wheel rim, as well as their rather demanding physical properties, are considered herein to be well known to those skilled in such art.
Its rubber composition is conventionally composed, for example, of cis 1,4-polyisoprene and cis 1,4-polybutadiene rubber(s) in order to have good abrasion resistance and durability.
A particular concern for fabrication of the tire components, particularly the chafer rubber composition in the actual building of the tire is the green strength of the chafer rubber composition. The green strength of the chafer rubber in its uncured state is considered herein to be significantly important because it helps to keep the components in the bead area of the tire in position prior to curing.
It should be pointed out that it has been previously proposed to use trans 1,4-polybutadiene rubber in various components of a tire such as its tread and sidewall components.
However, it is not known to the inventors where trans 1,4-polybutadiene rubber is used in pneumatic tire chafer composition in a manner described herein.
Considerations of prior suggestions of use of trans 1,4-polybutadiene in tires may be found, for example, in U.S. Pat. No. 5,386,865.